Plasma processing apparatuses that propagate microwaves from slots formed in a Radial Line Slot Antenna (RLSA) into a processing container and generate plasma are conventionally used in, for example, film formation or etching (for example, see Japanese Laid-Open Patent Publication No. 2006-107994). These RLSA-type plasma processing apparatuses are capable of forming uniform plasma having high density and a low electron temperature, and thus plasma-process large-sized semiconductor wafers uniformly and fast.
In the RLSA, a plurality of slot arrays each having a plurality of slots are arranged in concentric circles. The RLSA tries to uniformize plasma density generated in a processing chamber by adjusting an interval between adjacent slot arrays and the size of each of the slots.